Method of making tubes



June 18, c H. wA s ,METHOD OF MAKING TUBES Filed June 21, l 1934Patented June 18, 1935 UNITED STATES 2,005,306 METHOD OF MAKING TUBESClarence H. Wallis, Ellwood City, Pa., assignor to National-TubeCompany, a. corporation of New Jersey 7 Application June 21, 1934,Serial no. 731,793

4 Claims.

This invention is a method of making seamless steel tubes with cleaninside surfaces.

Such tubes are nowmade by hot and cold working the metal to tubes of thegage desired. These tubes are then annealed, after which their insidesurfaces are washed and dried with great care and their opposite endssolidly pointed in an effort to keep these surfaces clean. The tubes arethen externally coated with lubricant, sunk to the proper outsidediameters by being drawn through i a die, this including annealing andpickling as required, are finally annealed to obtain the p y icalcharacteristics desired, and are finished. Finishing includesstraightening and cutting to length, the cutting removing the tubessolidly pointed ends.

Every precaution is taken to prevent the inside surfaces of the tubesfrom being contaminated by the lubricant after they have been washedclean upon the completion of their final drawing. The solid pointing oftheir ends is intended to exclude the lubricant and to protect theirinside surfaces from dirt and the action of the oxygen in the air.However, trouble is experienced in that the drying of their insidesurfaces cannot be done quickly enough, after they have been cleaned bywashing, to prevent the formation of rust. Furthermore, some air isnecessarily entrapped during the solid pointing of their ends, and thisair oxidizes their inside surfaces during the subsequent annealingoperations.

Referring to the accompanying drawing:

Figure 1 illustrates a tube.

Figure 2 shows this tube after its ends have been pointed.

Figure 3 shows the removal of the pointed ends of this tube.

According to the present invention, lubricant is used on the last colddrawing pass of the tubes over a mandrel, which is characterized in thatit will not deposit a residue when heated to annealing temperatures.Such a lubricant may be a soap-tallow lubricant which is substituted forthe fiour-tallow lubricant customarily used. Specifically speaking, sucha lubricant may consist of approximately ten per cent soap stock andeight per cent tallow substitute, mixed with eighty-two per cent water.The tallow substitute contains heavy mineral oil and degras.

After the tubes have received their last cold drawing pass, theiropposite ends are solidly pointed with the described lubricant still ontheir inside surfaces. That is to say, their inside surfaces are notcleaned. The solidly pointed tubes are then' annealed to remove thestresses created by this cold working, and it is particularly at thisstage that the advantages of the lubricant come into play. Thus, becauseof its described characteristic, it does not deposit a residue upon theinside surfaces of the tubes but is instead oxidized to a fine,nonadhesive powder. Furthermore, since the lubricant is oxidized by theair entrapped in these tubes, the oxygen content in this air is removed.

It is consequently obvious that the tubes inside surfaces do not becomeoxidized, and that they can be finished simply by cutting off theirsolidly pointed ends, the usual straightening operation being, ofcourse, included. The tubes then have perfectly clean inside surfaces.

Usually the tubes must be sunk to smaller outside diameters. When thisis done, the solidly pointed and annealed tubes are pickled and washedin the usual manner, it being noted that this does not affect theirinside surfaces because their pointed ends exclude all fluids. They arethen doped with lubricant and sunk to the required outside diameters byone or more passes with intermediate annealing and pickling, asrequired, after which they are given a final anneal for the purposes ofimparting the desired physical characteristics, straightened, and theirpointed ends removed.

In the drawing, Figure 1 shows a tube l as it appears when ready forpointing, Figure 2 shows the tube I with its ends pointed, as at 2,. soas to close its inside. Figure 3 shows the removal of the pointed endsby means of saws 3.

vThe specific details connected with these various stages have alreadybeen described.

It is to be noted that the method is not only better than the standardpractice, in that it produces pipes with cleaner inside surfaces, butthat it is quicker in that the careful washing and drying steps areeliminated. The flour-tallow lubricant usually used cannot be utilizedin the final drawing stage of the new process because it deposits aresidue when heated to annealing temperatures. Soap-tallow, on the otherhand, does not deposit such a residue and, in addition absorbs theoxygen in the air entrapped by the solid" pointing of the tubes so thatthis ordinarily objectionable atmosphere becomes essentially reducing incharacter whereby the inside surfaces of the tubes are protected.

I claim:

1. A method of making seamless tubes with clean inside surfaces,including using a lubricant on their last cold drawing passes over amandrel,

which will not deposit a residue when heated to posite ends of saidtubes after said last cold drawing passes without cleaning their insidesurfaces, subsequently annealing said tubes and then finishing saidtubes including cutting 01! their solid- 1y pointed ends.

2. A method of making seamless tubes with clean inside surfaces,including using a. lubricant on their last cold drawing passes over amandrel, which will not deposit a residue when heated to annealingtemperatures, solidly pointing the opposite ends of said tubes aftersaid last cold drawing passes without cleaning their inside surfaces,subsequently annealing said tubes, then sinking said tubes to therequired outside diameters and finishing said tubes including cuttingoil their solidly pointed ends.

3. A method of making seamless tubes with clean inside surfaces,including using a soap- 2,005,306 annealing tempeatures, solidlypointing the optallow lubricant on their last cold drawing passes over amandrel, solidly pointing the opposite ends of said tubes after saidlast cold drawing passes without cleaning their inside surfaces,subsequently annealing said tubes and then finishing said tubesincluding cutting off their solidly pointed ends.

4. A method of making seamless tubes with clean inside surfaces,including using a soaptallow lubricant on their last cold drawing passesover a mandrel, solidly pointing the opposite ends of said tubes aftersaid last cold drawing passes without cleaning their inside surfaces,subsequently annealing said tubes, then sinking said tubes to therequired outside diameters and finishing said tubes including cuttingofi their solid- 1y pointed ends.

CLARENCE H. WALLIS

